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United States Patent |
6,080,883
|
Schnurr
,   et al.
|
June 27, 2000
|
Method of simultaneously producing 6-aminocapronitrile and
hexamethylenediamine
Abstract
A process for the coproduction of 6-aminocapronitrile (ACN) and
hexamethylenediamine (HMD) by treatment of adiponitrile (ADN) with
hydrogen in the presence of a nickel-containing catalyst at temperatures
not below room temperature and elevated hydrogen partial pressure in the
presence or absence of a solvent comprises, after the conversion based on
ADN and/or the selectivity based on ACN has or have dropped below a
defined value
(a) interrupting the treatment of ADN with hydrogen by stopping the feed of
ADN and of the solvent, if used,
(b) treating the catalyst at from 150 to 400.degree. C. with hydrogen using
a hydrogen pressure within the range from 0.1 to 30 MPa and a treatment
time within the range from 2 to 48 h, and
(c) then continuing the hydrogenation of ADN with the treated catalyst of
stage (b).
Inventors:
|
Schnurr; Werner (Herxheim, DE);
Voit; Guido (Schriesheim, DE);
Flick; Klemens (Herxheim, DE);
Melder; Johann-Peter (Neuhofen, DE);
Fischer; Rolf (Heidelberg, DE);
Harder; Wolfgang (Weinheim, DE)
|
Assignee:
|
BASF Aktiengesellschaft (Ludwigshafen, DE)
|
Appl. No.:
|
155900 |
Filed:
|
October 8, 1998 |
PCT Filed:
|
April 4, 1997
|
PCT NO:
|
PCT/EP97/01685
|
371 Date:
|
October 8, 1998
|
102(e) Date:
|
October 8, 1998
|
PCT PUB.NO.:
|
WO97/37964 |
PCT PUB. Date:
|
October 16, 1997 |
Current U.S. Class: |
558/452; 558/459 |
Intern'l Class: |
C07C 255/00 |
Field of Search: |
558/452,459
|
References Cited
U.S. Patent Documents
2208598 | Jul., 1940 | Rigby.
| |
2762835 | Sep., 1956 | Swerdioff.
| |
5310713 | May., 1994 | Kojima et al.
| |
5827938 | Oct., 1998 | Schnurr et al. | 558/459.
|
Foreign Patent Documents |
61 942 | Sep., 1982 | EP.
| |
2 284 163 | May., 1995 | GB.
| |
92/21650 | Dec., 1992 | WO.
| |
Other References
Jrl. Of Catalysis 143, 187-200 (193) 187-200.
Catal. Rev. Sci. Eng. 16(2), 155-189 (1977).
|
Primary Examiner: Richter; Johann
Assistant Examiner: Murray; Joseph
Attorney, Agent or Firm: Keil & Weinkauf
Parent Case Text
This Application is a 371 of PCT EP 97/01685 Apr. 4, 1997.
Claims
What is claimed is:
1. A process for the coproduction of 6-aminocapronitrile (ACN) and
hexamethylenediamine (HMD) by treatment of adiponitrile (ADN) with
hydrogen in the presence of a nickel-containing catalyst at temperatures
not below room temperature and elevated hydrogen partial pressure in the
presence or absence of a solvent, which comprises, after the conversion
based on ADN and/or the selectivity based on ACN has or have dropped below
a defined value
(a) interrupting the treatment of ADN with hydrogen by stopping the feed of
ADN and of the solvent, if used,
(b) treating the catalyst at from 150 to 400.degree. C. with hydrogen using
a hydrogen pressure within the range from 0.1 to 30 MPa and a treatment
time within the range from 2 to 48 h, and
(c) then continuing the hydrogenation of ADN with the treated catalyst of
stage (b).
2. A process as claimed in claim 1, wherein the treatment of ADN with
hydrogen is carried out in suspension at a temperature within the range
from 40 to 150.degree. C. and a pressure within the range from 2 to 20
MPa.
3. A process as claimed in claim 1, wherein the treatment of ADN with
hydrogen is carried out in a fixed-bed reactor in a downflow or upflow
process at a temperature within the range from 20 to 150.degree. C. and a
pressure within the range from 2 to 30 MPa.
4. A process as claimed in claim 2, wherein, following interruption of the
treatment of ADN with hydrogen (stage (a)) and before the treatment of the
catalyst with hydrogen (stage (b)), the catalyst is rinsed with liquid
ammonia and, after the rinse, the ammonia is displaced with an inert gas.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an improved process for the co-production
of 6-aminocapronitrile (ACN) and hexamethylenediamine (HMD) by treatment
of adiponitrile (ADN) with hydrogen in the presence of a nickel-containing
catalyst at temperatures not below room temperature and elevated hydrogen
partial pressure in the presence or absence of a solvent.
The present invention further relates to a process wherein the treatment of
ADN is carried out in suspension or in a fixed bed in a downflow or
outflow process.
The hydrogenation of ADN to 6-aminocapronitrile in the presence of
solvents, especially ammonia, and nickel-containing catalysts has been
described in detail for example in U.S. Pat. No. 2,762,835, U.S. Pat. No.
2,208,598 and WO 92/21650.
The nickel-containing catalysts used in the hydrogenation of ADN lose
activity in long runs and therefore have to be replaced with new catalysts
once the activity has dropped below a certain value.
Nickel-containing catalysts are widely used in industry for steam
reforming, for methanization and for the hydrogenation of functional
groups such as CO double bonds, C--C multiple bonds or nitrile groups. In
many of the aforementioned applications the catalyst is deactivated sooner
or later through the formation of carbonaceous deposits on the active
catalyst surface. The formation of carbonaceous deposits in steam
reforming and the removal of these layers by reaction with oxygen,
hydrogen, steam or carbon dioxide is described in Trimm, Catal. Rev.Sci.
Eng., 16(2), 155-187 (1977). Measurable reaction rates are achieved with
hydrogen only at temperatures above 550.degree. C.
The regeneration of catalysts coated with carbonaceous deposits is
generally effected by burning off the organic coatings with nitrogen-air
mixtures. However, this method can be used only with catalysts which
remain stable on reaction with air supported catalysts with a stable
structure of oxidic material, such as SiO.sub.2, Al.sub.2 O.sub.3,
TiO.sub.2, can be successfully regenerated by this method. For instance,
GB-A 2,284,163 describes the regeneration of a supported catalyst with Pt,
Pd, Ru, Rh, etc. or nickel by treatment of [sic] a gas containing at least
chlorine and oxygen.
Catalysts with very high metal contents become damaged on burning off the
organic deposits with air, altering their mechanical properties (see EP-A
61,042).
EP-A 61,042 also discloses that nickel-containing catalysts having a
maximum nickel content of 50% by weight for the hydrogenation of
butynediol to butanediol can be regenerated by hydrogen treatment at
temperatures between 200 and 500.degree. C., preferably at temperatures
above 275.degree. C.
Similarly, U.S. Pat. No. 5,310,713 describes a regeneration with hydrogen
for an alkylation catalyst which may contain nickel, but the regeneration
with hydrogen is carried out in the presence of liquid alkane and of a
chloride source.
It is known from Journal of Catalysis 143 (1993), 187-200, that a nickel
catalyst (25% by weight of Ni on SiO.sub.2) which is used for the
hydrogenation of acetonitrile in the gas phase can be regenerated by
treatment with hydrogen at temperatures of above 200.degree. C.
The cited references do not reveal whether it is also possible to
regenerate nickel-containing catalysts used in the hydrogenation of higher
boiling dinitriles, especially adiponitrile. For bi-functional compounds
such as dinitriles, in particular, can give rise, under reaction
conditions, to the formation of oligomers which lead to regeneration
problems.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process whereby it is
possible to regenerate the nickel-containing catalysts used in
hydrogenation of ADN to ACN and HMD in a simple way, without incurring
long shutdown times during the regeneration of the catalysts. More
particularly, the object is to raise catalyst activity in respect of
conversion and selectivity in the hydrogenation of ADN as closely as
possible to the level of the unused catalyst.
We have found that these objects are achieved by a process for the
coproduction of 6-aminocapronitrile (ACN) and hexamethylenediamine (HMD)
by treatment of adiponitrile (ADN) with hydrogen in the presence of a
nickel-containing catalyst at temperatures not below room temperature and
elevated hydrogen partial pressure in the presence or absence of a
solvent, which comprises, after the conversion based on ADN and/or the
selectivity based on ACN has or have dropped below a defined value
(a) interrupting the treatment of ADN with hydrogen by stopping the feed of
ADN and of the solvent, if used,
(b) treating the catalyst at from 150 to 400.degree. C. with hydrogen using
a hydrogen pressure within the range from 0.1 to 30 MPa and a treatment
time within the range from 2 to 48 h, and
(c) then continuing the hydrogenation of ADN with the treated catalyst of
stage (b).
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The nickel catalysts used can be customary Raney nickel catalysts (as
fixed-bed or suspension catalysts) or supported catalysts. Raney nickel
catalysts are known and commercially available or preparable in a known
manner from a nickel-aluminum alloy by treatment with a base such as
sodium hydroxide solution. The support used may typically be alumina,
silica, activated carbons, titania and zirconia. Supported catalysts
customarily have a nickel content within the range from 3 to 95,
preferably 20 to 95, especially from 50 to 95, % by weight, based on the
total mass of nickel and support.
The catalysts may also be modified, if desired, with metals of group VIB
(Cr, Mo, W) and VIII of the periodic table (Fe, Ru, Os, Co, Rh, Ir, Pd,
Pt) and also with copper, rhenium or manganese, in which case the nickel
content of the catalyst is generally within the range from 50 to 99.9,
preferably from 80 to 99, % by weight, based on the active components
(nickel+modifier).
Furthermore, the catalysts may be modified with a compound based on an
alkali metal or an alkaline earth metal such as lithium, sodium,
potassium, rubidium, cesium, magnesium, calcium, strontium and barium,
especially cesium. It is customary to use a weight ratio within the range
from 0 to 5, preferably from 0.1 to 3, % by weight of alkali metal or
alkaline earth metal to nickel.
The nickel catalysts usable according to the invention may be prepared in
various ways. The preparation of supported nickel catalysts is customarily
effected by impregnating a ceramic support with an aqueous organic
solution of a nickel salt and, if desired, the modifier, then drying and
calcining in a conventional manner. The solubility of the salts and pore
volume of the support limits, according to observations to date, the
amount of nickel which can be applied by one impregnating step, so that,
if desired, the impregnating procedure may have to be repeated more than
once, in which case, in general, the catalyst is dried and calcined after
each impregnating step in order that the desired level of nickel may be
obtained on the catalyst. It is also possible to apply nickel by
precipitation of a sparingly soluble nickel compound such as the
corresponding hydroxide or carbonate compound to a support suspended in
the precipitation solution. The precipitates can be shaped in a
conventional manner, customarily after filtration or spray drying.
The hydrogenations can be carried out with preference in upflow, downflow
or suspension processes.
When the reaction is carried out in a suspension, it is customary to choose
temperatures within the range from 40 to 150.degree. C. preferably within
the range from 50 to 100.degree. C., particularly preferably within the
range from 60 to 90.degree. C.; the pressure is generally chosen to be
within the range from 2 to 20, preferably 3 to 10, particularly preferably
from 4 to 9, MPa. The residence times are essentially dependent on the
desired yield, selectivity and the desired conversion; customarily, the
residence time is selected so as to maximize the yield, for example within
the range from 50 to 275, preferably within the range from 70 to 200, min.
In the suspension process, the solvent used is preferably ammonia, amines,
diamines and triamines having from 1 to 6 carbon atoms such as
trimethylamine, triethylamine, tripropylamine and tributylamine or
alcohols, especially methanol and ethanol, particularly preferably
ammonia. It is advantageous to use a dinitrile concentration within the
range from 10 to 90, preferably from 30 to 80, particularly preferably
from 40 to 70, % by weight, based on the sum of dinitrile and solvent.
The amount of catalyst used is generally within the range from 1 to 50,
preferably from 5 to 20, % by weight, based on the amount of dinitrile
used.
The suspension hydrogenation can be carried out batchwise or, preferably,
continuously, generally in the liquid phase. The hydrogenation may also be
carried out batchwise or continuously in a downflow or upflow process in a
fixed-bed reactor, in which case it is customary to employ a temperature
within the range from 20 to 150.degree. C., preferably within the range
from 30 to 90.degree. C., and a pressure generally within the range from 2
to 30, preferably within the range from 3 to 20, MPa. The hydrogenation is
preferably carried out in the presence of a solvent, preferably ammonia,
amines, diamines and triamines having from 1 to 6 carbon atoms such as
trimethylamine, triethylamine, tripropylamine and tributylamine or
alcohol, preferably methanol and ethanol, particularly preferably ammonia.
In a preferred embodiment, the amount of ammonia used is within the range
from 0.5 to 10, preferably from 1 to 6, g per g of adiponitrile.
Preference is given to using a catalyst space velocity within the range
from 0.1 to 2.0, preferably from 0.3 to 1.0, kg of adiponitrile/l*h. Here
too it is possible to adjust the conversion and hence the selectivity in a
specific manner by varying the residence time.
The hydrogenation can be carried out in a customary suitable reactor.
If the reaction is carried out in the gas phase, it is customary to use
temperatures within the range from 100 to 250.degree. C., preferably
within the range from 160 to 200.degree. C.; the pressure employed is
generally within the range from 0.01 to 3, preferably from 0.09 to 0.5,
MPa. Furthermore, the molar ratio of hydrogen to ADN is generally within
the range from 2:1 to 300:1, preferably within the range from 10:1 to
200:1.
In a preferred embodiment, the hydrogenation of ADN is carried out in the
presence of ammonia as solvent using fixed-bed catalysts as described
above by a process wherein, following the deactivation of the catalyst,
ie. a decrease in the conversion of ADN and/or selectivity based on ACN
below a defined value, first the feed of adiponitrile and ammonia is
switched off, then the temperature is brought to 200-250.degree. C., and
subsequently the catalyst is treated for from five to six hours with from
200 to 800, preferably from 500 to 700, especially 600, l of hydrogen/l of
cat. x h. Thereafter the temperature is customarily brought back down to
reaction temperature and the hydrogenation is continued.
Prior to starting the regeneration, it is preferable to remove the
hydrogenation mixture still present in the reactor. It may further be
advantageous, especially if the treatment of the ADN with hydrogen is
carried out in suspension, to wash the catalyst before the actual
regeneration, ie. after interruption of the treatment of ADN with hydrogen
(stage (a)) and before treatment with hydrogen (stage (b)), with the
solvent present in the system, especially with liquid ammonia. The wash
temperature employed is customarily within the range from 20 to
200.degree. C., especially within the range from 20 to 100.degree. C. It
is generally advantageous to carry on the wash for a period of from 2 to
24 hours.
From experience to date, the regeneration can be carried out at any desired
time. From an economic point of view, a regeneration appears to be
sensible when the conversion based on ADN and/or the selectivity based on
ACN has dropped by more than 10%, based on the initial value.
According to the invention, the regeneration of the catalyst is carried out
at temperatures within the range from 150 to 400.degree. C., preferably
within the range from 180 to 270.degree. C., especially within the range
from 200 to 250 .degree. C., using a hydrogen pressure within the range
from 0.1 to 30 MPa, preferably within the range from 0.1 to 20 MPa, and a
treatment time within the range from 2 to 48 h, preferably within the
range from 2 to 24 h. A continuous process is customarily carried out with
the hydrogen rate within the range from 100 to 1500, preferably within the
range from 200 to 1000, l of hydrogen/l of reactor volume.times.hour.
The process of the invention makes it possible to achieve distinct
improvements in the life and space-time yield of nickel catalysts in the
hydrogenation of adiponitrile to 6-aminocapronitrile and
hexamethylenediamine (nylon 6 and nylon 66 intermedates).
EXAMPLES
Example 1
(Suspension Hydrogenation)
Reactor: 250 ml autoclave with sampling port (material of construction: HC
4); agitation by disk stirrer.
Batch: in each case 48 g of ADN, 5.6 g of Raney nickel (BASF, H 1-50,
water-moist).
Raney nickel was introduced into an autoclave under a protective gas
(argon). The autoclave was then sealed and 150 ml of liquid NH.sub.3 were
injected. After brief stirring, the bulk of the ammonia was pressed out of
the reactor via a riser pipe equipped with a frit. This process was
repeated six times with 50 ml of liquid ammonia each time to obtain
anhydrous Raney nickel as a representative starter catalyst (ammonia
holdup about 100 ml). Thereafter the system was heated to 80.degree. C.,
48 g of adiponitrile were metered in, and the pressure was raised with
hydrogen to 7 MPa. Catalyst-free samples of the liquid phase were removed
through the sampling port after 20, 45, 90, 135, 180 and 225 min.
After 225 min, the temperature in the reactor was reduced to 25.degree. C.
and the catalyst-free reaction mixture was removed. The catalyst remaining
in the reactor was rinsed six times with 50 ml of liquid ammonia each
time, at room temperature, by the method described for the wash prior to
the first use. For the subsequent run the system was heated back up to
80.degree. C. and the reactants were metered in afresh. The runs with
sampling and washing were repeated a number of times.
Table 1 shows the conversion of the adiponitrile and the selectivity to
6-aminocapronitrile as evident from the GC data after a hydrogenation time
of 225 min. Apart from ACN, hexamethylenediamine was formed almost
exclusively.
TABLE 1
______________________________________
Run ADN conversion
ACN selectivity
______________________________________
1 84.2 59.6
2 49.6 70.4
3 43.4 64.7
4 37.3 70.1
5 30.6 75.2
6 29.2 75.2
7 26.3 77.2
8 24.2 80.0
9 17.3 79.5
10 16.2 85.0
11 13.2 81.6
12 9.0 86.8
13 7.4 95.3
14 6.0 85.5
15 5.3 84.6
16 5.4 87.2
17 4.9 90.3
18 5.8 88.2
______________________________________
Following run 18, the hydrogenation mixture was removed and the deactivated
catalyst was rinsed six times with liquid ammonia. Thereafter the ammonia
was completely decompressed and entirely displaced from the reactor using
argon. The reactor was then heated to 100.degree. C. and once more flushed
with argon. The argon was then displaced by flushing with hydrogen. The
reactor was then heated to 250.degree. C. and the pressure set with
hydrogen to 10 MPa. The reactor was left at 250.degree. C. for 5 hours.
The autoclave was then led down to room temperature, the gas phase was
completely depressed, and the next block of runs was started.
TABLE 2
______________________________________
Run after regeneration of catalyst
Run ADN conversion
ACN selectivity
______________________________________
19 54.9 80.5
______________________________________
Regeneration with hydrogen made it possible to raise the conversion based
on ADN from 5.8% to 54.9%.
Example 2
(Continuous Gas Phase Hydrogenation)
Catalyst preparation: 4 mm Al.sub.2 O.sub.3 extrudates (SPH 512 B, Rhone
Poulenc) were initially impregnated for two hours at room temperature with
an aqueous, 3.5% strength by weight CsNO.sub.3 solution, then air-dried at
120.degree. C. for 16 h and subsequently calcined in air at 350.degree. C.
over 4 h. The extrudates thus calcined were then impregnated with an
aqueous, 44.3% strength by weight Ni(NO.sub.3).sub.2 solution for 2 h,
then air-dried at 120.degree. C. for 16 h and subsequently calcined in air
at 350.degree. C. over 4 h. Thereafter the impregnation, drying and
calcining was repeated with the nickel salt solution.
After cooling, the extrudates were installed in a reduction apparatus and
flushed for 2 h at room temperature with 20 l/h of N.sub.2 to remove air.
This was followed by heating to 300.degree. C. with a heating rate of
2.degree. C./ min and a hydrogen flow of 20 l/h of H.sub.2 and the
300.degree. C. were maintained for 20 h.
The catalyst thus prepared contained 0.1% by weight of Cs and 13% by weight
of Ni, based on the total weight of the extrudates.
Hydrogenation:
40 g/h of adiponitrile were introduced into a vaporizer (280.degree. C.)
and passed from there with 400 l/h of hydrogen through a tubular reactor
(packed with 330 g of catalyst; reactor dimensions: length=2000 mm,
diameter=15 mm) in the downflow direction. The reactor temperature was
180.degree. C. The gaseous reactor effluent was condensed in cold traps
and analyzed by gas chromatography. Following a startup phase, the
adiponitrile conversion obtained was 45.2%, which dropped to 24.1% over a
period of 445 h. The aminocapronitrile selectivity was within the range
from 80 to 90%.
The dinitrile feed was then turned off and the catalyst regenerated in the
reactor with 200 l/h of hydrogen at 250.degree. C. over 6 hours. Following
renewed startup under identical conditions (see above), a conversion of
42.7% was obtained; that is, the catalyst had almost been restored to its
initial activity.
Example 3
(Fixed-bed Hydrogenation in the Liquid Phase)
Catalyst preparation
2.5 kg of an NiAl alloy (from BASF, H1-55) were impregnated at 80.degree.
C. with stearic acid. After comminution of the cooled and solidified mass,
the powder obtained was pressed into tablets (3 mm height, 3 mm diameter).
The tablets thus obtained were then calcined at 900.degree. C. over 2 h.
The activation of the tablets was carried out with sodium hydroxide
solution. For this, 2.4 kg of the tablets were introduced into 5.7 l of
water and then admixed with vigorous stirring to a total of 1.44 kg of
NaOH platelets. On completion of the addition the stirring was continued
at 90.degree. C. for a further 24 h. After cooling, the activated tablets
were washed with water until the wash liquor was pH-neutral.
The activated catalyst tablets were installed in the reactor under water
and rinsed with ammonia.
Hydrogenation
370 g/h of adiponitrile and 1.1 kg/h of ammonia were passed with 500 l/h of
hydrogen through a tubular reactor (packed with 740 ml of catalyst;
length=1800 mm, diameter 30 mm) in the upflow direction. The reactor
temperature was 50.degree. C., the pressure was 20 MPa. The reactor
effluent was analyzed by gas chromatography. Following a startup phase an
adiponitrile conversion of 45% was obtained, which dropped to 20% over a
period of 280 hours. The aminocapronitrile selectivity rose from initially
80 to 90%.
The dinitrile and ammonia feed were then switched off and the catalyst
regenerated in the reactor at 200.degree. C. and a hydrogen pressure of 20
MPa (at 500 l/h of hydrogen) for 5 hours. After renewed startup under
identical conditions (see above) the conversion rose to 45% (at an ACN
selectivity of 80%); that is, the catalyst had been restored to its
initial activity.
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